1. Field of the Invention
This invention belongs to the domain of electronic devices including an element visible on a face and the manufacturing methods of such a device. An electronic device is understood in the following description as an assembly formed by insulating layers in which at least an electronic element is incorporated. In particular the present invention concerns portable electronic devices, e.g. electronic cards or electronic tokens.
The present invention deals with a specific electronic device comprising a visible electronic element connected to an internal module. The visible element is defined here either as a fixed electronic component such as a visual display, a fingerprint sensor, a membrane switch, a contact module, a solar cell, a buzzer or any other similar element, or as a removable component such as a battery. This element can be connected to an internal module situated between two layers of insulating material that constitute the device faces.
The internal module situated inside the device is formed by one (such as an antenna) or several components connected to one another that serve to define the device functions. For example, in a device in the form of a payment card without contact, the internal module is formed by a chip or electronic circuit connected to an antenna. Furthermore, it can be connected to a display visible on one of the faces of the card allowing the visualization of data contained in the internal module such as the amount available or the debits carried out.
An electronic device of this type is generally made up of the arrangement of an internal module on or over a first sheet made from an insulating material and includes a window in which an electronic component is lodged. The internal module is then connected to the component and then, in general, coated or covered with a resin before laminating a second insulating sheet that will be stacked on the resin. The device manufactured in this way is a sandwich made up of at least two insulating sheets between which the internal module incorporated in a binder layer is arranged. The external face of the electronic component lodged in the window appears on one of the exterior faces of the device.
2. Description of the Prior Art
For example the document FR 2760113 describes a manufacturing method of a combined card that can function with or without contact. The element that maintains the contacts is placed in a cavity formed by a window cut out of a substrate and with a bottom made up of an adhesive sheet on which the substrate is placed. An antenna is connected to the element conductive areas, then the assembly is covered with a binder before the application of an insulating protection film. The adhesive sheet on the first face of the card is removed at the end of the manufacturing process thus allowing the appearance of the contacts on the card surface.
According to this method, various manufactured devices are rejected during the final control of production because they include residues of filling resin close to the window where the electronic component is situated. In fact, for example, when the outline of the window is larger than that of the component, the resin fills the space left between the outlines of the window and the component and thus the resin can spill out over the exterior face of the device. In other cases, the structure of the component can contain grooves which the resin can infiltrate by capillary effect and contaminate the device surface. This type of device is discarded, or otherwise a supplementary cleaning operation would be necessary to eliminate the binding residue.
When the contact element constitutes an autonomous component that is to say without connection to an antenna or to other components, it can be pressed in the profiled frame of a window formed in a substrate with a thickness at least equal to that of the component. The document JP03114788 describes a method for inserting a contact element in the substrate of a card that including a profiled window in such a way to hold the element on the surface of one of the faces of the card. The element is held in the window on the face opposite to the contacts by an insulating sheet provided with reliefs fitted onto the rear face of the element.
Another document EP1085459 describes a manufacturing method for a contact memory card where the contact element is inserted into a profiled frame formed in the first part of a substrate. A second flat substrate adhered to the first constitutes the bottom of a cavity delimited by the outline of the frame serving to support the contact element. The latter is inserted into the cavity in such a way that the contacts level the surface of the face of the first substrate.